Golf club groove configuration

ABSTRACT

The present invention is directed to a golf club head, and a method of making the golf club head, with an improved striking surface. The grooves are formed in the strike surface with tight tolerances. The grooves may contain a plurality of portions, including a radiused or angled portion, a portion having substantially parallel walls, and a portion having a v-shape.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. patent application Ser. No.12/477,570, filed on Jun. 3, 2009, now pending, which is acontinuation-in-part of U.S. patent application Ser. No. 11/711,096,filed on Feb. 27, 2007, now pending, which is a continuation-in-part ofU.S. patent application Ser. No. 10/902,064, filed on Jul. 30, 2004, nowU.S. Pat. No. 7,273,422, which are incorporated herein by reference intheir entireties.

This application claims the benefit of U.S. Provisional PatentApplication No. 60/528,708 filed on Dec. 12, 2003, which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to golf clubs. In particular, the presentinvention relates to a golf club head having an improved strikingsurface.

2. Description of the Related Art

Golf club heads come in many different forms and makes, such as wood- ormetal-type, iron-type (including wedge-type club heads), utility- orspecialty-type, and putter-type. Each of these styles has a prescribedfunction and make-up.

Iron-type and utility-type golf club heads generally include a front orstriking face, a top line, and a sole. The front face interfaces withand strikes the golf ball. A plurality of grooves, sometimes referred toas “score lines,” is provided on the face to assist in imparting spin tothe ball. The top line is generally configured to have a particular lookto the golfer and to provide structural rigidity for the striking face.A portion of the face may have an area with a different type of surfacetreatment that extends fractionally beyond the score line extents. Someclub heads have the surface treatment wrap onto the top line. The soleof the golf club is particularly important to the golf shot because itcontacts and interacts with the ground during the swing.

In conventional sets of iron-type golf clubs, each club includes a shaftwith a club head attached to one end and a grip attached to the otherend. The club head includes a face for striking a golf ball. The anglebetween the face and a vertical plane is called the loft angle.

The United States Golf Association (USGA) publishes and maintains theRules of Golf, which govern golf in the United States. Appendix II tothe USGA Rules provides several limitations for golf clubs. For example,the width of a groove cannot exceed 0.035 inch, the depth of a groovecannot exceed 0.020 inch, and the surface roughness within the areawhere impact is intended must not exceed that of decorativesand-blasting or of fine milling. The Royal and Ancient Golf Club of StAndrews, which is the governing authority for the rules of golf outsidethe United States, provides similar limitations to golf club design.

U.S. Pat. No. 6,814,673 is directed to grooves for iron-type golf clubs.However, the grooves are poorly engineered.

SUMMARY OF THE INVENTION

The present invention relates to golf clubs. In particular, the presentinvention relates to a golf club head having an improved strikingsurface. The golf club head of the present invention has a flat strikingface, preferably being milled. This allows a greater degree of flatnessthan typically seen. Preferably, the face is flat within ±0.002 inch.Grooves or score lines are then cut into the flattened face. Typically,grooves are formed in the face as part of the head-forming process. Forexample, if the head is cast, typical grooves are formed as part of thecasting process. The face—including the grooves—is then subject topost-casting process steps, such as polishing. Similar finishing stepsare also typically performed on club heads that are formed by forging.Machining grooves in the face after it has been milled beneficiallysaves them from being affected by any face post-manufacturing processes,which can adversely affect, for example, the groove-face interface,making it inconsistent along the length of the groove.

Preferably, the grooves are angled or otherwise ramped from theirmaximum depth into the face to the face surface at the groove ends. Thishelps facilitate cleaning sand, dirt, and other debris from the grooves.This may be characterized in a variety of manners. For example, themaximum depth distance of the groove (that is, the non-ramped, ornon-radiused, portion of the groove) versus the overall length of thegroove. In one preferred embodiment, the overall groove length is atleast 0.25 inch longer than the maximum depth distance. As anotherexample, the grooves may be radiused at toe and heel portions of thegolf club head, a preferred radius range being from 0.125 inch to 5inches. The maximum depth of the grooves may be about 0.02 inch deep ata geometric center of the face.

The grooves of the present invention preferably are formed by spinmilling or fly cutting. Forming the grooves in this manner allows fortighter draft angles, increases the rate of production, and allows fortighter tolerances than casting or forging. Preferably, the draft angleof the inventive grooves is between about 0.5° and 12°. The grooves maybe formed by a round cutter, preferably having a diameter from ⅜ inch to¾ inch. A preferred draft angle range is from about 0.5° to 12°.

The surface of the club face may be textured or roughened. Providing atextured strike face allows the golfer to apply more friction to theball during use, allowing the golfer to put more spin on the ball andhave greater control of the ball. Preferably, the surface has asubstantially uniform textured surface with a roughness greater than 40Ra. The face may be selectively textured to enhance certain shots thatthe golfer may perform. This may include providing a plurality ofdistinct sets of texturing to accommodate a plurality of differentshots. This selectively directional texturing may include the texturingstep, preferably milling, in a single direction.

The present invention also includes a method of making the golf clubhead described above. One preferred method includes forming a golf clubhead in known fashion, such as casting or forging. The strike face,which does not yet contain any grooves, is then machined to besubstantially flat. Grooves are then machined in the face, and the faceis roughened. These last two steps may be performed individually, ineither order, or they may be performed simultaneously.

The club head of the present invention may contain grooves having aplurality of portions. A first portion adjacent to and interacting withthe club head strike face may be radiused or angled relative to thestrike face. A second portion, adjacent to the first portion, may bedefined by substantially parallel walls that are substantiallyperpendicular to the strike face. A third portion may have an v-shapeand be angled at approximately 90°. A fourth section may be curved,having a small radius, to join the walls of the third portion.

DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the accompanyingdrawings, in which like reference characters reference like elements,and wherein:

FIG. 1 shows a golf club head of the present invention;

FIG. 2 shows a cross-sectional view of a club head of the presentinvention along a groove;

FIG. 3 shows a preferred groove cutting setup;

FIG. 4 shows a comparison of a groove of the golf club head of FIG. 1 asviewed along lines 4-4 of FIG. 2 with a known groove;

FIG. 5 shows a comparison of a groove of the golf club of FIG. 1 and aknown groove;

FIGS. 6-10 each show a cross-section of a preferred groove of thepresent invention;

FIG. 11 illustrates a step in a method of making grooves in accordancewith the present invention;

FIG. 12 illustrates another step in a method of making grooves inaccordance with the present invention;

FIG. 13 illustrates an embodiment of another step in a method of makinggrooves in accordance with the present invention; and

FIGS. 14 and 15 illustrate another embodiment of a step in a method ofmaking grooves in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Other than in the operating examples, or unless otherwise expresslyspecified, all of the numerical ranges, amounts, values and percentagessuch as those for amounts of materials, moments of inertias, center ofgravity locations, loft and draft angles, and others in the followingportion of the specification may be read as if prefaced by the word“about” even though the term “about” may not expressly appear with thevalue, amount, or range. Accordingly, unless indicated to the contrary,the numerical parameters set forth in the following specification andattached claims are approximations that may vary depending upon thedesired properties sought to be obtained by the present invention. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claims, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Furthermore, when numerical ranges ofvarying scope are set forth herein, it is contemplated that anycombination of these values inclusive of the recited values may be used.

The present invention is directed to a golf club head with an improvedstriking surface. FIG. 1 shows a golf club head 1 of the presentinvention. The golf club head 1 includes a body 10 defining a frontsurface 11, a sole 13, a top line 14, a heel 15, a toe 16, and a hosel17. The striking face of the front surface 11, which contains grooves 12therein, and the sole 13 may be unitary with the body 10, or they may beseparate bodies, such as inserts, coupled thereto. While the club head 1is illustrated as an iron-type golf club head, the present invention mayalso pertain to a utility-type golf club head or a wood-type club head.

FIG. 2 shows a cross-sectional view of the club head 1 along a groove12. Grooves 12 are machined into the surface of the striking face 11,which allows the draft angle to be decreased. Grooves 12 extend from atoe end of the club head 1 to a heel end of the club head 1. The grooves12 are shallow at both the toe and heel portions of the club head 1, andare deep in the central regions. Grooves 12 have a first distance d1measured along the surface of striking face 11 and a second distance d2measured along the deepest portion of the grooves, which have a depthd3. Thus, first distance d1 is an overall distance and second distanced2 is a maximum depth distance. Preferably, the groove depth along themaximum depth distance d2 is substantially constant. In one embodimentthe maximum depth distance d2 is at least 0.25 inch shorter than theoverall distance d1. The groove draft angle α ranges from about 0.5° to12°, more preferably about from 4° to 6°, and most preferably 5°.

Grooves 12 are radiused at the toe and heel portions of the club head 1,and are about 0.02 inch deep at a geometric center of the face 11.Grooves 12 are machined into the strike face surface 11. The club head 1is retained in a mold, which preferably is formed of a material softenough to not damage the club head 1 yet resilient enough to firmlyretain the golf club head 1, and a cutter, preferably a round cutter ora saw cutter, is used to form the grooves 12. As sown, the toe and heelportions are radiused about an axis of rotation that is perpendicular toa longitudinal axis of the groove. Furthermore, that axis of rotation isapproximately parallel to face 11 of club head 1. Preferred cutters havea diameter from ⅜ inch to ¾ inch. A preferred range of groove radiiinclude from 0.125 inch to 5 inches, with 0.25 inch to 2.5 inches beingmore preferred. Having radiused grooves 12 facilitates removal of dirt,grass, sand, and other materials that typically become embedded withinthe grooves of a golf club during normal use by eliminating corners thatcan trap these materials. FIG. 3 shows a preferred groove cutting setupillustrating cutter 20 with groove 12.

Machining the grooves 12, in addition to decreasing the draft angle,increases the rate of production and allows for tighter tolerances thancasting or forging. The rate of production is increased by decreasingthe number of required manufacturing steps. Instead of inserting thetool into the club face, machining the grooves, and removing the toolfrom the club face in three separate steps, as required by known groovecreating processes, the present invention allows all three to becombined into one step. This is possible because the turning axis of thepresent cutter is parallel to the face, rather than the perpendicularaxes of known processes. By orienting the turning axis of the cutter sothat it is parallel to the face allows the groove profile to be createdby building that profile into the edge of the cutter. As a result,complex groove geometries and tightly controlled dimensions, includingthe edge radius, may be created. The tighter tolerances possible withthe present invention allow less material to be removed, also decreasingmanufacturing time. FIG. 4 shows a comparison of a groove 12 of thepresent invention with a typical groove 22 of known golf club heads. Thegroove 12 preferably has a depth of 0.02 inch, which is the USGA limit.Due to loose tolerances, known grooves 22 were designed well short ofthis limit. Similarly, known manufacturing processes required a largedraft angle β, typically around 16°. The draft angle α of grooves 12 ismuch smaller, increasing the cross-sectional area of the groove andgroove volume for a given length.

As noted above, the governing bodies of golf place limitations on thegeometry of grooves 12. The increased tolerance control afforded bymachining the grooves 12 of the present invention allows the actualgroove geometry to be closer to the limits than was previouslyachievable. Thus, the grooves 12 of the present invention maximizegroove volume, enhancing the groove performance during use. With theimproved grooves of the present invention, the grooves better grip theball, allowing a golfer to apply more spin to the ball. The golfer'scontrol over the ball, both during ball flight and subsequent to flight,such as when landing and settling on a golf green, are increased. Thegrooves 12 of the present invention also result in a golf club head thatis more aesthetically pleasing and that allows better ball control.

FIG. 5 shows a comparison of a groove 12 of the present invention with atypical groove 22 of known golf club heads. The known grooves 22 arequite rounded. The grooves 12 of the present invention, however, aremuch sharper. The edges are more defined, the depth is greater, and thedimensions are more consistent and closer to the limits. All of thesefactors allow the golf club head 1 to better grip the golf ball,increasing the user's control over the ball.

The face 11 of the club head 1 of the present invention is also enhancedto provide additional ball control and enhanced performance. The strikesurface 11 is provided with a roughened texture. A common measure ofroughness in surface finish is average roughness, Ra. Ra, also known asArithmetic Average (AA) and Center Line Average (CLA), is a measure ofthe distance from the peaks and valleys to the center line or mean. Itis calculated as the integral of the absolute value of the roughnessprofile height over the evaluation length:

${Ra} = {\frac{1}{L}{\int_{0}^{L}{{{r(x)}}{x}}}}$

The face 11 is roughened by machining, preferably with a ComputerNumerically Controlled (CNC) mill. Known golf clubs have a faceroughness at most 40 Ra. At least a portion of the face 11 in theproximity of the grooves, and more preferably the entire face 11, ismachined such that it has a substantially uniform textured surface witha roughness greater than 40 Ra. Preferably, the roughness is from 75 Rato 300 Ra, more preferably from 100 Ra to 200 Ra, and most preferablyfrom 120 Ra to 180 Ra.

Providing a textured strike face allows the golfer to apply morefriction to the ball during use, allowing the golfer to put more spin onthe ball and have greater control of the ball. Conventionally, golfershave to take a full swing to induce enough golf ball spin to control theball movement on a golf green. With the golf club head of the presentinvention, a golfer can induce golf ball spin in “partial” shots, orshots when the golfer is not taking a full swing. The textured strikesurface of the present invention also distributes the shear forceresulting from the golf swing over a greater area of the golf ball. Thisreduces cover damage and extends golf ball life.

The golf club head 1 preferably is formed of a soft base metal, such asa soft carbon steel, 8620 carbon steel being an example. A chrome finishmay be applied to the base metal to inhibit wear and corrosion of thebase metal. If included, the chrome finish preferably includes anon-glare layer. The chrome finish layer preferably has a thicknessbetween 0.005 μin and 280 μin, with 80 μin a preferred thickness. Anickel finish may additionally be applied to the base metal as asub-layer for chrome or another finish layer or may alternatively beapplied to the base metal as the finish layer. If included, the nickelfinish preferably has a thickness between 400 μin and 1200 μin, with 800μin a preferred thickness.

In use, the grooves 12 and strike face 11 of the present inventionenhance performance, especially in adverse conditions. The higherfriction possible with the golf club head 1 allows a tighter grip on thegolf ball during “wet” or “grassy” conditions than was previouslypossible. The club head of the present invention was tested, and asshown in Table 1 below, the generated revolutions per minute of a struckgolf ball were substantially the same as those generated with aconventional club for a full dry shot, but were increased in a half dryshot and in both a full wet shot and a half wet shot. The “dry” shotscontained substantially no moisture on the club face and ball. For the“wet” shots, the club face and/or the golf ball surface were sprayedwith water in an amount that would be typical for shots made during around in dewy or rainy conditions. A 60° wedge was used in these tests.Table 1 shows the revolutions per minute of a golf ball after beingstruck with a standard club or a spin milled club of the presentinvention, and illustrates the benefit of the spin milled grooves overstandard grooves.

TABLE 1 Shot Conditions Standard Spin Milled Dry - full 12250 12000Dry - half 6500 7750 Wet - full 8000 12000 Wet - half 4000 8000

A preferred method of making the club head 1 includes first making aclub head body. This may be done by casting, forging, or any othermanufacturing method. The face is then machined such that it issubstantially smooth and flat, preferably flat within ±0.002 inch. Thispreferably may be done by fly-cutting the face, which is cutting with asingle-point tool fixed to the end of an arm protruding from a verticalmilling shaft. For example, a fly-cutter may be used to create a flatface, as shown in FIG. 11. Having a flat face allows the golfer toachieve consistent results during use. The body preferably is nestedduring the face flattening process. That is, the body is retained withina housing such that it is substantially immobile. The face is leftexposed so that it can be worked on. The housing may be padded orotherwise designed such that it does not damage the club head.

Once the requisite face flatness has been achieved, the grooves arecreated and the surface is roughened as described above. While it ispreferred that the grooves be spin milled prior to roughening thesurface, the order of these steps is not essential. In fact, it ispossible that they be performed substantially simultaneously, or with atleast some amount of overlap.

The spin milled grooves may have very sharp edges, which could have anadverse effect on a golf ball during use. Thus, the grooves may bedeburred to remove any sharp edges in the groove-to-face junction. Thiscreates a radius at the junction, the radius preferably being less than0.01 inch. This deburring can be carried out in a variety of ways. Thejunction may be filed, such as with a wire brush or a file, such as acarbide file. In conjunction with filing, or as an alternative method,the junction can be deburred by blasting. This may include impactingsmall beads at the junction at high speeds. To protect the face of theclub head, which may have already been roughened above 40 Ra, the facemay be masked. Masking includes placing a physical barrier on the faceadjacent the grooves such that the projected particles cannot impact theface. Alternatively or in conjunction with masking, a nozzle can be usedto accurately direct the projected material only at the junction. As astill further alternative, or additionally, a cutting tool that includesthe desired edge profile may be utilized. For example, the profile ofthe cutting tool may be configured to match the desired groove profile.

Another process that may be employed in the method of making club head 1is using a forming, or shaping, die to alter the dimensions of rough cutgrooves by displacing material adjacent the rough cut grooves.Generally, grooves in the face of a golf club are difficult tomanufacture to tight tolerances which makes it difficult to createrepeatable, highly precise groove dimensions. Additionally, it makes itdifficult to mass-produce golf clubs that take full advantage of theexacting standards of the rules placed on grooves by the USGA and theR&A. According to the present invention, a precisely shaped die ispressed or stamped into a rough cut groove to alter desired attributesof the groove. The die is made to very tight tolerances so that theresultant groove has dimensions that are tightly controlled. The die maybe used to alter a particular portion of the groove or it may be used toalter the entire groove geometry.

A method of producing a groove using a die is generally illustrated inFIGS. 11-13. In an embodiment, the method includes a step of producing aflat face on golf club head 1, as illustrated in FIG. 11. Duringmanufacture of golf club head 1, the club head is generally initiallyformed by casting or forging and the club head is formed with a facethat is intended to be flat. However, because of manufacturingtolerances face 11 is not as flat as may be desired. In order toincrease the flatness of face 11, a cutting tool 34 may be used. Cuttingtool 34 may be a fly-cutter that is generally rotated along an axis thatis substantially normal to the face and then passed laterally across theface to reduce and remove the deviations in the face flatness, as shown.The step of increasing the flatness of face 11 may be performed beforeor after rough cut grooves 32 are formed in face 11. The process mayalso be used as a final process after the final groove configuration iscreated.

FIG. 12 illustrates the creation of rough cut grooves 32 using a cuttingtool 36, which is illustrated as a spin mill cutter. Rough cut grooves32 are grooves that are cut into face 11 that do not have the finaldesired dimensions. In an embodiment, rough cut grooves 32 havingparallel side walls and sharp corners at the edge where the grooveinterfaces with face 11 are created using a spin mill cutter. If leftunaltered, rough cut grooves 32 may not comply with the USGA or R&Arules because the sharp edges at the interface with face 11 would notcomply with established rules for edge dimensions. Rough cut grooves 32may be created by various methods. Preferably, the rough cut grooves arespin milled into the face of club head 1, but they may alternatively becast, end milled, rough stamped or forged, cut with a laser or waterjet, or assembled using material layering. The rough cut grooves mayhave any desired configuration, such as a U-groove, V-groove or afaceted groove.

Referring to FIG. 13, after club head 1 is provided with rough cutgrooves 32, a forming die 38 is pressed into rough cut grooves 32 toalter, or create, features in the rough cut grooves 32 which creates afinal groove configuration having tight tolerances and a repeatableconfiguration. For example, the operation may be used to create a radiusor facet in the edge material at the interface between face 11 and theside wall of rough cut groove 32 so that a final desired groove edge iscreated, such as an edge that conforms to USGA and/or R&A rules.Additionally, or as an alternative, the stamping operation may be usedto create side walls that have a desired draft angle or to preciselycontrol the width of each groove. Preferably, using die 38 the toleranceof the edge radius of the grooves may be controlled to +/−0.0005 inchand the tolerance on the draft angle may be controlled to +/−0.2degrees.

Die 38 includes projections 40 that are pressed into rough cut grooves32 to shape the material that is adjacent the grooves and that definesthe grooves. Projections 40 are precisely shaped so that they shape thematerial to a desired shape. As a result, when it is desired tomanufacture grooves that comply with USGA or R&A rules, using a dieallows the manufactured groove dimensions to more closely match thelimits of the rules more consistently. In addition, by pressing thematerial around the groove using die 38, the edges of the groove becomework hardened which may increase the wear resistance of the groove. Inembodiments using die 38 to alter the sides or edges of the grooves, thelength D₄ of projections 40 is preferably less than the depth D₅ ofrough cut grooves 32 so that projection 40 remains spaced from a bottomsurface of the groove. However, it should be appreciated that length D₄of projections 40 may be greater than the depth of rough cut grooves 32if die 38 is used to control the final depth of the grooves or to createfeatures in the bottom surface of the grooves. Furthermore, the processof using die 38 to form the grooves may include using a plurality ofdies or multi-piece dies that progressively shape rough cut groove 32into the final desired configuration.

Texturing may also be added to the club head face using a die. Referringto FIGS. 14 and 15, a die 68 includes surface texturing features 66 thatare pressed into club head 1 and form surface texturing, or supplementsurface texturing from another operation. Texturing features 66 may beincluded on any portion of die 68 that contacts club head 1. Forexample, texturing features 66 may be included adjacent projections 70so that texturing is created on strike face 11 when die 68 is pressedagainst club head 1. In addition, or as an alternative, surfacetexturing may be created on an internal portion of the grooves byincluding texturing features 66 on a corresponding portion of one ormore projections 70. In an embodiment, texturing is created in the edgematerial of one or more grooves at the interface between the strike face11 and the groove side wall so that texturing is provided on the edgeradius or facet. Alternatively, a separate die or die portion, such asin a multi-piece die, may be included that includes texturing features.The texturing features may be pressed into portions of the groovesand/or into the spaces between grooves simultaneously with shaping thegrooves or as a separate operation. Face texturing generally includesteeth, ridges, dimples, symbols, dots, numbers, or any other shapedfeature that alters the face contour.

The die may be constructed using any precise machining method and ispreferably constructed from material having high wear resistance. Forexample, [please provide examples of materials and machining methods fordie]

FIGS. 6-10 each show a cross-section of a preferred faceted groove 12that may be formed by the methods described above. The groove 12includes a first portion 121 adjacent to and interacting with the clubface 11. In some embodiments, the edges of the groove 12 have beendeburred, either having a radius or being angled. Preferably, the radiusor angled edge is created using a spin milling tool that has the featureincorporated into the complementary cutting profile. In embodimentsincorporating an angled edge, such as those of FIGS. 6-9, a preferredrange of angles A₁ is about 10° to 50°. In embodiments incorporating aradiused first portion, the radius is preferably less than 0.015 inchand more preferably less than 0.010 inch. The width W₁ of the groove 12at the strike face 11, which is generally the widest portion of thegroove 12 and the maximum groove width, is between about 0.030 inch toabout 0.045 inch, and is preferably about 0.035 inch. The widthtransitions narrower through the first groove portion 121 to a width W₂that is between about 0.033 and about 0.020 inch at the lowermostboundary of the first portion 121, also referred to as the distal end ofthe first portion 121. The first portions of the illustrated embodimentsof FIGS. 6-10 are similar, but extend to varying depths D₁. Theembodiment illustrated in FIG. 6 has the shallowest depth D₁, and theembodiment illustrated in FIG. 10 has the deepest depth D₁. The firstportion 121 has a depth D₁ between about 0.001 and 0.008, preferablyhaving a depth D₁ of approximately 0.005 inch, with 0.001 to 0.003 inchbeing more preferred. In some preferred embodiments, the first portion121 has a depth D₁ that is about 20% to about 40% of the overall groovedepth D, and more preferably about 35% of the overall groove depth D.The overall groove depth D preferably is between about 0.0150 and 0.0225inch, more preferably about 0.02 inch.

The groove 12 includes a second portion 122 adjacent to the firstportion 121. Second portion 122 preferably has substantially parallelwalls that are substantially perpendicular to the face 11,“substantially” herein meaning the walls may be angled at an angle A₂ ofup to about 20°. Preferably, the walls defining the second portion 122are spaced as far apart as possible to maximize the volume of the groove12. A preferred range of widths W₂, W₃ is about 0.033 to 0.027 inch. Inrelative terms, the width W₂ at a proximal end of second portion 122 isthe maximum width of the second portion 122 and is preferably from about80% to 98% of the maximum groove width W₁. Preferably, the width W₃ at adistal end, or the bottom portion, of the second portion 122 is at leastabout 80% of the width W₂ at a top portion of the second portion 122. Apreferred range of depths D₂ is between about 0.003 inch and about 0.008inch. In some embodiments, the second section depth D₂ is at least halfthe overall groove depth D. In other embodiments, however, the secondportion 122 has a depth D₂ that is about 15% to about 35% of the overallgroove depth D.

The groove 12 includes a third portion 123 adjacent to the secondportion 122 and further distal from face 11. This portion 123 has aV-shape, having angled side walls each having an internal angle A₃ ofabout 35° to about 55°, as measured from a plane normal to face 11.Thus, the width of the third portion 123 decreases from a proximal end,or the top portion thereof (nearest the face 11), to the distal end, orbottom portion thereof. Preferably, the width at the bottom of the thirdportion is less than about half of the width of the top portion. In somepreferred embodiments, the depth D₃ of the third portion 123 may be fromabout 0.006 inch to about 0.015 inch. The depth D₃ of the third portion123 preferably is at least twice the depth D₂ of the second portion 122.In some preferred embodiments, the third portion 123 has a depth D₃ thatis about 35% to about 55% of the overall groove depth D.

The groove 12 includes a fourth portion 124 adjacent to the thirdportion 123 that extends between the angled side walls of the thirdportion 123. This portion 124 may be radiused to join the walls of thethird section 123. A preferred radius R₄ is less than 0.012 inch. Inother embodiments, the fourth portion 124 includes a substantiallyplanar portion that extends between the opposite angled side walls ofthe third portion 123. The planar portion may intersect one or bothangled side wall of the third portion 123 at a radius R₄. In embodimentsincluding a planar fourth portion 124, the width W₄ of that portion ispreferably about 0.002 inch to about 0.010 inch, and more preferablyabout 0.006 inch.

Grooves 12, like the faceted groove shown in FIG. 10, were testedagainst V-shaped grooves on wedges having a static loft angle of 60° byplayers hitting golf balls out of the rough. The players had club headswings in a range of 50 mph to 80 mph. The tested V-grooves includedangled side walls having an internal angle of about 38°.

For each of the players, the faceted grooves of the present inventionincreased back spin over the V-grooves. Generally, the spin rateincreased between about 8% to about 41% for club head speeds in thatrange. Table 2 shows the revolutions per minute of a golf ball afterbeing struck with the test club having V-grooves and the test clubhaving grooves of the present invention for various swing speeds.

TABLE 2 Swing Speed V-Groove Faceted Groove % Increase 57 mph 2480 26808% 65 mph 2610 3690 41% 72 mph 2960 3780 28%

Portions of the golf clubs of the present invention may also be hardenedto increase wear resistance. As a result, the grooves are more resistantto dimensional changes caused by use. Preferably, the club head materialadjacent the grooves is hardened. The hardness is increased by applyingextremely high heat to at least a portion of the golf club head andsubsequently quenching the golf club head. For example, localizedhardening of the material may be accomplished by applying extremely highlocalized heating, such as with a laser, and subsequently oil quenchingthe golf club head.

In an embodiment, only the material on a side of each of the groovesnearest a top line of the golf club head is hardened. For example, thegolf club head includes a hardened portion that extends from the side ofeach groove about 0.05 inch toward the top line. The depth of eachhardened portion is generally less than or equal to about 0.005 inchdeep from the club face. Preferably, the depth tapers from a thickestportion adjacent the groove. In an example, a golf club head constructedof carbon steel having a hardness of about 90 on the Rockwell Hardness Bscale and includes localized hardened portions, such as those describedabove, that have a hardness of about 45 on the Rockwell Hardness Cscale.

While the preferred embodiments of the present invention have beendescribed above, it should be understood that they have been presentedby way of example only, and not of limitation. It will be apparent topersons skilled in the relevant art that various changes in form anddetail can be made therein without departing from the spirit and scopeof the invention. Thus, the present invention should not be limited bythe above-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

1. A method of making a golf club head, comprising: providing a golfclub head body having a face and a rough cut groove disposed therein;providing a die having a projection; and pressing the projection intothe rough cut groove to displace material adjacent the groove.
 2. Themethod of claim 1, further comprising machining the face so that it issubstantially flat.
 3. The method of claim 1, wherein the step ofpressing the projection into the rough cut groove includes displacingedge material at an interface between the rough cut groove and the face.4. The method of claim 2, wherein the edge material is displaced to forma radius.
 5. The method of claim 2, wherein the edge material isdisplaced to form a facet.
 6. The method of claim 2, wherein the diecomprises surface texture features and the edge material is displaced bythe surface texture features.
 7. The method of claim 1, wherein the stepof pressing the projection into the rough cut groove includes displacingthe material forming side walls of the rough cut groove to form a draftangle.
 8. The method of claim 1, wherein the die comprises surfacetexture features.
 9. The method of claim 9, further comprising pressingthe surface texture features into the face.
 10. A method of making agolf club head, comprising: providing a golf club head body having aface; forming a rough cut groove in the face; providing a die having aprojection; and pressing the projection into the rough cut groove todisplace material adjacent the groove.
 11. The method of claim 10,further comprising machining the face so that it is substantially flat.12. The method of claim 10, wherein the step of forming a rough cutgroove includes spin milling the groove.
 13. The method of claim 10,wherein the step of forming a rough cut groove includes machining therough cut groove into the face such that the groove contains alongitudinal axis and the groove is radiused at toe and heel portions ofthe golf club head about axes of rotation that are perpendicular to thelongitudinal axis.
 14. The method of claim 10, wherein the step offorming a rough cut groove includes casting the groove.
 15. The methodof claim 10, wherein the step of forming a rough cut groove includesforging the groove.
 16. The method of claim 10, wherein the step offorming a rough cut groove includes milling the groove.
 17. A method ofmaking a golf club head, comprising: providing a golf club head bodyhaving a face; machining the face so that it is substantially flat; spinmilling a plurality of rough cut grooves into the face; providing a diehaving a plurality of projections; and pressing the plurality ofprojections into the plurality of rough cut grooves to displace materialadjacent the groove.
 18. The method of claim 17, wherein the diecomprises surface texture features and the step of pressing theplurality of projections into the plurality of rough cut grooves furthercomprises pressing the surface texture features into the face.
 19. Themethod of claim 17, wherein the step of pressing the plurality ofprojections into the plurality of rough cut groove includes displacingedge material at an interface between the rough cut grooves and theface, and wherein the edge material is displaced to form a radius. 20.The method of claim 17, wherein the step of pressing the plurality ofprojections into the plurality of rough cut groove includes displacingedge material at an interface between the rough cut grooves and theface, and wherein the edge material is displaced to form a facet.